Field
The present disclosure relates to telecommunications apparatus and methods, for example mobile communications networks and methods for communicating data using mobile communications networks, infrastructure equipment for mobile communications networks, communications devices for communicating data via mobile communications networks and methods of communicating via mobile communications networks.
Description of Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention.
It is well known in the field of wireless telecommunications for regions of the radio spectrum to be assigned to different mobile network operators (MNO) for their exclusive use through a license. A license typically grants an MNO exclusive use over a number of years of a predefined portion of the radio frequency spectrum in which to deploy a mobile communications network (e.g. GSM, WCDMA/HSPA, LTE/LTE-A). This licensing approach can help guarantee Quality of Service (QoS) and provides an operator with control of the radio resources and mobility. In particular, an operator has some degree of guarantee that no other radio services should interfere with the radio resources that have been assigned to the operator, and within the limitations of the license conditions the operator has exclusive control over what radio technology it deploys in the network. Consequently, a wireless telecommunications system that is primarily designed to operate using radio resources that have been licensed for exclusive use by the wireless telecommunications system can operate with a degree of centralised control and coordination to you a full help make most efficient use of the available radio resources. Such a wireless telecommunication system can also manage interference internally, based on standard specifications, since the licence grants it a degree of immunity from external interference sources. Coexistence of different devices deployed on an MNO's licensed band can be managed through conformance to relevant radio standards. Licensed spectrum is today usually assigned to operators via government-organised auctions, but so-called “beauty contests” continue also to be in use.
It is also well known in the field of wireless telecommunications for regions of the available radio spectrum to remain unlicensed. Unlicensed (licence exempt) radio spectrum may, at least to some extent, be freely used by a number of different technologies, such as Wi-Fi and Bluetooth and other non-3GPP radio access technologies (RATs). Operating parameters for devices using unlicensed spectrum bands are typically stipulated by technical regulatory requirements, e.g. the FCC Part 15 rule for 2.4 GHz ISM band. Coexistence of different devices deployed on an unlicensed band generally lacks centralised coordination and control and so is usually based on such technical rules and various politeness protocols.
The use of wireless telecommunications system technologies designed for operation on licensed radio spectrum, such as LTE, is becoming more and more prevalent, both in terms of increasing take-up of established uses for wireless telecommunications technologies, and also the introduction of new uses, e.g., in the developing field of machine-type communications (MTC). In order to help provide more bandwidth to support this increased use of wireless telecommunications technologies, it has recently been proposed to use unlicensed radio spectrum resources to support operations on licensed radio spectrum.
However, in contrast to licensed spectrum, unlicensed spectrum can be shared and used among different technologies, or different networks using the same technology, without any co-ordinated/centralised control, for example to provide protection against interference. As a consequence of this, the use of wireless technologies in unlicensed spectrum can be subject to unpredictable interference with no guarantees of spectrum resource availability and radio connections taking place on a best effort basis. Thus the operation of wireless network technologies on shared radio resource spectrum (such as unlicensed spectrum) can be impacted by the operation of other radio access technologies, such as wireless local area networks, and conversely the operation of such other radio access technologies can be impacted by the operation of the wireless network technologies on the shared portions of the radio spectrum.
For example, an LTE-based wireless telecommunications network that is able to make use of radio resources shared with a wireless local area network radio access technology (WLAN) could potentially prevent a WLAN access point from operating properly, at least temporarily. For example, certain WLAN radio access technologies, such as Wi-Fi, operate on a “listen-before-talk” basis to help manage access to the shared resources. Basically, a device operating on the WLAN that wishes to access certain radio resources will first monitor the radio resources to determine if they are currently available or already in use. An LTE-based wireless telecommunications network may be configured to adopt a similar “listen-before-talk” approach in respect of its communications on shared radio resources to seek to avoid making transmissions on resources currently being used for WLAN communications. However, an issue with this approach can arise because of differences in typical coverage areas associated with WLAN access points and LTE base stations. For example, an LTE base station may be too far from a WLAN access point to be able to detect ongoing WLAN communications associated with the WLAN access point but the WLAN access point may nonetheless be within the coverage area of the LTE base station downlink signals. Accordingly, a base station implementing a “listen-before-talk” approach to help govern its access to shared radio resources may not be able to detect communications associated with the WLAN access point when the base station is monitoring the relevant radio resource usage by other devices (“listen”). Accordingly, the base station may conclude it is free to transmit (“talk”) on radio resources which are being used by the WLAN access point, thereby interfering with the WLAN access point and potentially making it unavailable while the LTE base station is transmitting. In some respects this may be referred to as a “hidden node” issue.
These types of issue mean that wireless network technologies, such as LTE, which are generally designed to operate using licensed radio resources, may benefit from modified approaches to allow them to efficiently use shared radio resources, and in particular to co-exist reliably and fairly with other radio access technologies accessing the shared resources. Therefore, deploying a mobile radio access technology system primarily designed to operate in licensed spectrum bands (i.e. having exclusive access to, and hence a level of control over, the relevant radio resources) in a manner which is required by operation in a shared/unlicensed spectrum band (i.e. without having exclusive access to at least some of the relevant radio resources), gives rise to new technical challenges.